JP6107298B2 - Electrophotographic photosensitive member, electrophotographic process cartridge, and image forming apparatus - Google Patents

Description

The present invention relates to a photoreceptor having at least a photosensitive layer, and more specifically, an electrophotographic photoreceptor having good image characteristics such as filming, and good electrical characteristics including repetition at normal temperature and normal humidity and high temperature and high humidity.
The present invention also relates to an image forming apparatus having the photoreceptor and a cartridge.

In recent years, electrophotographic technology has been widely used and applied not only in the field of copying machines but also in the field of various printers because of its immediacy and high-quality images.
As for photoconductors that are the core of electrophotographic technology, in recent years, photoconductors using organic photoconductive materials that have the advantages of non-polluting, easy film formation, easy manufacture, etc. Has been developed. In particular, a stacked type photoconductor composed of a charge generation layer and a charge transfer layer, which separates the function of absorbing light to generate charges and the function of transporting the generated charges, has become the mainstream. Currently, these photoreceptors are widely used in the field of image forming apparatuses such as copying machines and laser printers.

The electrophotographic photosensitive member has a basic structure in which a photosensitive layer is formed on a conductive support. For the purpose of improving wear resistance and the like, a surface protective layer is sometimes provided on the photosensitive layer.
In general, in order to form an image by electrophotography, a toner image is formed by charging, image exposure and development on the surface of a photoreceptor, and the toner image is transferred and fixed on a transfer material to obtain an image. This photoreceptor is used repeatedly over a long period of time after residual toner is cleaned. If the cleaning is not performed well, the residual toner adheres to the photoreceptor and causes image defects (filming). In recent years, low-temperature fixing toner has been used for the purpose of energy saving in image forming apparatuses, and from the viewpoint of improving image quality, toner having a large sphericity and a small particle size has been used, and filming is more likely to occur. Therefore, repeated electrical characteristics in each environment are also good, and suppressing filming images is a major issue.

  As a countermeasure against filming, a surface protective layer or a charge transport layer of a plurality of charge transport layers is provided. For example, as a surface protective layer, a technique (Patent Document 1) containing microcapsules containing lubricating oil in the surface protective layer, a trimethylolpropane acrylate crosslinked product, a cured organosilica film, and heat or light There exists a technique (patent document 2) containing a crosslinked type crosslinked body.

  As a technique for containing fine particles in the surface protective layer, a technique for containing fine particles such as titanium oxide and tin oxide in the surface protective layer and setting the absorbance per 1 μm of the film thickness of the surface protective layer to a specific value (Patent Document 3) ), A technique (Patent Document 4) containing a radical polymerizable monomer, a crosslinkable resin and a filler in the surface protective layer, and a technique (Patent Documents 5 to 7) containing silica particles in the surface protective layer.

As the mobility in the surface protective layer, the surface protective layer contains silica particles, and a technique (Patent Document 8) in which the charge transport layer thickness / charge transport layer mobility is defined, two charge transport layers are provided, and the upper layer The (outermost surface layer) contains a filler such as alumina particles, the lower layer does not contain a filler, and the charge mobility of the lower layer containing no filler is 1.2 × 10 ⁵ when the electric field strength is 4 × 10 ⁵ V / cm. ^The technique which is more than ^-5 cm < ² > / V * sec is disclosed (patent documents 9-12).

On the other hand, if the outermost surface layer is a single-layer charge transport layer in a laminated photoconductor and can provide filming suppression effects without deteriorating electrical properties including repeated normal temperature and normal humidity and high temperature and high humidity, Since an extra step is not included in the process, there is a great cost advantage as compared with the case of forming a surface protective layer or a plurality of charge transport layers. For example, silicon oxide filler particles having a primary particle size of 100 nm or less are contained in the charge transport layer in an amount of 0.1 to 2% by mass in the total charge transport layer, and the mobility is 2 × 10 ⁵ (V / cm). The charge mobility is 5 × 10 ^-6 (cm ² / V · s) or higher, so it is excellent in mechanical / electrical durability and long-lasting with no abnormal image even when used repeatedly for a long time. A technique for obtaining a photoreceptor is disclosed (Patent Document 13). In Patent Literature 13, the silica primary particles are as small as 100 nm or less, and the content of silica particles is small.

  Photoreceptors that have good dispersion stability of the coating solution for surface layer formation, good productivity, and good electrical characteristics including repeated characteristics of normal temperature, normal humidity, and high temperature and high humidity, and are effective in suppressing filming. Did not exist.

JP 2006-99035 A JP 2008-26689 A JP 2003-140373 A JP 2012-98639 A Japanese Patent No. 3844258 Japanese Patent No. 3859086 Japanese Patent No. 4056097 JP 2001-281898 A JP 2002-258499 A JP 2003-98700 A JP 2002-229227 A JP 2002-351102 A JP 2010-250174 A

  According to the studies by the inventors, the structure described in Patent Document 13 is described as being excellent in mechanical properties, but the filming effect is not sufficiently obtained, and described in Patent Documents 1-12. The configuration has a problem in productivity because a surface protective layer or a plurality of charge transport layers are formed. In addition, when the charge transport layer is a single layer and the outermost surface layer, if a large amount of substances such as silica particles that hinder the flow of charge are contained, the repeated electrical characteristics deteriorate, the film becomes brittle, and the printing durability There was a problem of worsening sex. Further, in order to achieve high mobility, there is a means for increasing the content of the charge transport material, but if it is increased too much, there is a problem that the film becomes brittle and the printing durability deteriorates.

  The object of the present invention is that the coating solution for forming the charge transport layer has good stability over time, good productivity, excellent electrical characteristics including repeated characteristics of normal temperature and normal humidity, and high temperature and high humidity, and suppression of filming. An object is to provide an electrophotographic photosensitive member having an effect.

The object of the present invention is achieved by adopting one of the following configurations.
<1> In an electrophotographic photoreceptor having at least a charge generation layer and a charge transport layer in this order on a conductive substrate, the charge transport layer is a single layer and an outermost surface layer, and includes at least a charge transport material, a binder resin, and Silica particles having an average primary particle size of 0.2 to 1 μm, the silica particles being 5 to 15 wt% of the entire charge transport layer, and the hole mobility of the charge transport layer is an electric field strength of 2.0 × 10 ⁵ V An electrophotographic photosensitive member characterized by being 2.0 × 10 ⁻⁵ cm ² / V · s or higher at a temperature of 21 ° ^C./cm .
<2> The electrophotographic photosensitive member according to <1>, wherein the silica particles have an average primary particle size of 0.3 to 0.9 μm.
< 3 > The electrophotographic photosensitive member according to any one of <1> or <2>, wherein the silica particles are surface-treated with a reactive organosilicon compound.
< 4 > The electrophotographic photosensitive member according to any one of <1> to < 3 >, wherein the charge transport layer has a thickness of 10 μm or more.
< 5 > The charge polarizability α of the charge transport material is α> 100 (Å ³ ), and the dipole moment P is P <1.60 (D). The electrophotographic photosensitive member according to any one of 4 >.
< 6 > An image forming apparatus using the electrophotographic photosensitive member according to any one of < 1 > to <5> . < 7 > < 1 > to a cartridge for an image forming apparatus using the electrophotographic photosensitive member according to any one of <5> .

  According to the present invention, an electrophotography having good productivity, good stability of a coating solution for forming a charge transport layer, excellent electrical characteristics including repeated normal temperature and normal humidity and high temperature and high humidity, and capable of suppressing filming. A photoreceptor is obtained.

1 is a schematic diagram illustrating a main configuration of an embodiment of an image forming apparatus of the present invention.

Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is a representative example of the embodiments of the present invention, and is appropriately modified and implemented without departing from the spirit of the present invention. can do.
In the present invention, a charge generation layer is formed directly on a conductive support or a conductive layer, an undercoat layer, etc., and a single charge transport layer is formed on the charge generation layer. Become a layer.

<Electrophotographic photoreceptor>
The charge generation layer is formed directly on the conductive support or on the conductive layer, undercoat layer and the like. A single charge transport layer is formed on the charge generation layer, and the charge transport layer becomes the outermost surface layer. The photosensitive layer is either a single layer type or a sequential bilayer type in which a charge generation layer and a charge transport layer are laminated in this order. In the case of the forward bilayer type, the charge transport layer is a single layer. In the present invention, the charge transport layer (photosensitive layer in the case of a single layer) is the outermost surface layer.

<Conductive support>
There is no particular limitation on the conductive support, but for example, metal materials such as aluminum, aluminum alloy, stainless steel, copper, and nickel, and conductive powder such as metal, carbon, and tin oxide are added to impart conductivity. A resin material, a resin, glass, paper, or the like in which a conductive material such as aluminum, nickel, or ITO (indium tin oxide) is deposited or applied on the surface is mainly used. These may be used alone or in combination of two or more in any combination and ratio. As a form of the conductive support, a drum form, a sheet form, a belt form or the like is used. Furthermore, a conductive material having an appropriate resistance value may be used on a conductive support made of a metal material in order to control conductivity and surface properties and to cover defects.

Moreover, when using metal materials, such as an aluminum alloy, as an electroconductive support body, you may use, after giving an anodic oxide film. When an anodized film is applied, it is desirable to perform a sealing treatment by a known method.
The surface of the support may be smooth, or may be roughened by using a special cutting method or by performing a roughening treatment. Further, it may be roughened by mixing particles having an appropriate particle diameter with the material constituting the support. In order to reduce the cost, it is possible to use the drawing tube as it is without performing the cutting process.

<Underlayer>
In the present invention, the undercoat layer is not essential, but when an undercoat layer is provided, any undercoat layer can be provided. As the undercoat layer, a binder alone can be used, but it is preferable in terms of electrical characteristics and the like to contain an inorganic filler such as metal oxide particles.
As the metal oxide particles, those having high dispersion stability of the coating liquid are preferable, and specific examples include silica, alumina, titanium oxide, barium titanate, zinc oxide, lead oxide, and indium oxide. Among these, metal oxide particles exhibiting n-type semiconductor characteristics are preferable, titanium oxide, zinc oxide, and tin oxide are more preferable, and titanium oxide is most preferable.

Titanium oxide can be either crystalline or amorphous, but in the case of crystalline, the crystalline form may be any of anatase, rutile, or brookite, but anatase for reasons such as water absorption and surface treatment efficiency. A type or rutile type is generally used. Particularly preferably, a rutile type is used.
As for the particle size of the metal compound particles, those having an average particle size of usually 100 nm or less are preferable, and 10 to 60 nm is particularly preferable, for the reason of dispersion stability in the coating solution. The particle size of the particles used in the coating solution may be uniform or a composite system having different particle sizes. In the case of a composite system having different particle sizes, those having a maximum particle size peak near 150 nm and a particle size distribution with a minimum particle size of about 30 nm to about 500 nm are preferable. And 0.03 μm may be mixed and used.

  The metal oxide particles are preferably surface-treated with an organometallic compound or the like. The surface treatment can be produced by a dry method or a wet method. That is, in the dry method, it can be produced by a method in which a surface treatment agent is mixed with metal oxide particles to coat the metal oxide particles and, if necessary, heat treatment is performed. In the wet method, the metal oxide particles and a mixture of the surface treatment agent of the present invention mixed with an appropriate solvent are thoroughly stirred until they are uniformly attached or mixed with media, and then dried, if necessary. It can manufacture by the method of heat-processing.

  The surface treating agent is preferably a reactive organometallic compound. For example, methyl hydrogen polysiloxane, a silane treating agent having the following structure, and among them, methyldimethoxysilane is particularly preferable. A silane coupling agent having an acrylic group is also preferable, and 3-acryloxypropylmethoxysilane is particularly preferable.

(M is SiR ³ or the like, R is a hydrogen atom or an alkyl group, R ¹ and R ² are an alkyl group, and R ³ is an alkyl group or an alkoxy group)
Regarding the amount of the surface treatment agent, if the treatment amount is too small, the effect of the surface treatment cannot be obtained, and if the treatment amount is too large, there is a treatment agent that is not modified on the particle surface, and during the coating process, etc. This may cause repelling of the coating film. Therefore, the amount of the surface treatment agent is preferably adjusted according to the type of the metal oxide particles, and the lower limit is usually 0.3 parts by mass or more, preferably 1 part by mass with respect to the metal oxide particles used. On the other hand, the upper limit is usually 20 parts by mass or less, preferably 10 parts by mass or less.

  As the binder resin contained in the undercoat layer, resin materials such as polyvinyl acetal, polyamide resin, phenol resin, polyester, epoxy resin, polyurethane, and polyacrylic acid can be used. Among these, a polyamide resin having excellent adhesion to the support and low solubility in a solvent used in the charge generation layer coating solution is preferable. Among the polyamide resins, a copolymer polyamide having a cycloalkane ring structure as a constituent component is preferable, and a copolymer polyamide having a cyclohexane ring structure as a constituent component is more preferable. Among them, in particular, the following general formula (2) A copolymerized polyamide resin having the diamine component shown as a constituent material is preferred.

In formula (2), A and B each independently represent a cyclohexane ring which may have a substituent, and X represents a methylene group which may have a substituent.
The ratio between the metal oxide particles and the binder resin can be arbitrarily selected, but is 0.5 to 8 parts by mass with respect to 1 part by mass of the binder resin in terms of liquid stability, coatability, and electrical characteristics. The range is preferable, and the range of 2 parts by mass to 5 parts by mass is more preferable.

If the film thickness of the undercoat layer is too thin, the effect on local charging failure will not be sufficient, and conversely if it is too thick, the residual potential will increase or the adhesive strength between the conductive substrate and the photosensitive layer will decrease. Cause. In the present invention, the thickness of the undercoat layer is preferably 0.1 to 20 μm, more preferably 2 to 10 μm, still more preferably 3 to 6 μm.
The volume resistance value of the undercoat layer is usually 1 × 10 ¹¹ Ω · cm or more, preferably 1 × 10 ¹² Ω · cm or more, and usually 1 × 10 ¹⁴ Ω · cm or less, preferably 1 × 10 ¹³ Ω. -It is cm or less.

  In order to obtain an undercoating coating solution containing metal oxide particles and a binder resin, a metal oxide treated with a pulverization or dispersion treatment device such as a planetary mill, ball mill, sand mill, bead mill, paint shaker, attritor, or ultrasonic wave. The particle slurry may be mixed with a binder resin or a solution obtained by dissolving the binder resin in an appropriate solvent, and dissolved and stirred. Conversely, metal oxide particles may be added to the binder resin solution, and pulverization or dispersion treatment may be performed with the above-described dispersing apparatus.

<Charge generation layer>
The charge generation layer is formed by binding a charge generation material with a binder resin.
Examples of the charge generation material include inorganic photoconductive materials such as selenium and its alloys, cadmium sulfide, and organic photoconductive materials such as organic pigments, but organic photoconductive materials are preferred, especially organic pigments. Is preferred. Examples of organic pigments include phthalocyanine pigments, azo pigments, dithioketopyrrolopyrrole pigments, squalene (squarylium) pigments, quinacridone pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, anthanthrone pigments, and benzimidazole pigments. . Among these, phthalocyanine pigments or azo pigments are particularly preferable. When organic pigments are used as the charge generating substance, usually, fine particles of these organic pigments are used in the form of a dispersion layer bound with various binder resins.

  When a metal-free phthalocyanine compound or a metal-containing phthalocyanine compound is used as the charge generation material, a photosensitive member having a high sensitivity to a laser beam having a relatively long wavelength, for example, a laser beam having a wavelength around 780 nm, is obtained. When an azo pigment such as diazo or trisazo is used, it is sufficient for white light, laser light having a wavelength around 660 nm, or laser light having a relatively short wavelength, for example, laser having a wavelength around 450 nm or 400 nm. A photosensitive member having a high sensitivity can be obtained.

When an organic pigment is used as the charge generating material, a phthalocyanine pigment or an azo pigment is particularly preferable. The phthalocyanine pigment provides a photosensitive material with high sensitivity to a laser beam having a relatively long wavelength, and the azo pigment has a sufficient sensitivity to white light and a laser beam having a relatively short wavelength. , Each is excellent.
When using a phthalocyanine pigment as a charge generation material, specifically, metal-free phthalocyanine, copper, indium, gallium, tin, titanium, zinc, vanadium, silicon, germanium, aluminum or other metal or oxide thereof, halide, water Those having crystal forms of coordinated phthalocyanines such as oxides and alkoxides, and phthalocyanine dimers using oxygen atoms as bridging atoms are used. Particularly, titanyl phthalocyanines (also known as oxytitanium) such as X-type, τ-type metal-free phthalocyanine, A-type (also known as β-type), B-type (also known as α-type), and D-type (also known as Y-type), which are highly sensitive crystalline Phthalocyanine), vanadyl phthalocyanine, chloroindium phthalocyanine, hydroxyindium phthalocyanine, chlorogallium phthalocyanine such as type II, hydroxygallium phthalocyanine such as type V, μ-oxo-gallium phthalocyanine dimer such as type G and type I, type II, etc. The [mu] -oxo-aluminum phthalocyanine dimer is preferred.

  Among these phthalocyanines, A-type (also known as β-type), B-type (also known as α-type), and powder X-ray diffraction angle 2θ (± 0.2 °) are 27.1 ° or 27.3 °. D-type (Y-type) titanyl phthalocyanine, II-type chlorogallium phthalocyanine, V-type and 28.1 ° have the strongest peaks, and 26.2 ° have peaks A hydroxygallium phthalocyanine, G-type μ-oxo-gallium, having a clear peak at 28.1 ° and a half width W of 25.9 ° of 1 ° ≦ W ≦ 0.4 ° A phthalocyanine dimer and the like are particularly preferable.

  As the phthalocyanine compound, a single compound may be used, or several mixed or mixed crystals may be used. As the mixed state that can be put in the phthalocyanine compound or crystal state here, those obtained by mixing the respective constituent elements later may be used, or they may be mixed in the production / treatment process of the phthalocyanine compound such as synthesis, pigmentation, and crystallization. It may be the one that caused the condition. As such treatment, acid paste treatment, grinding treatment, solvent treatment and the like are known. In order to generate a mixed crystal state, as described in JP-A-10-48859, two types of crystals are mixed, mechanically ground and made amorphous, and then converted into a specific crystal state by solvent treatment. The method of doing is mentioned.

  When an azo pigment is used as the charge generation material, various bisazo pigments and trisazo pigments are preferably used. When an organic pigment is used as the charge generation material, one kind may be used alone, or two or more kinds of pigments may be mixed and used. In this case, it is preferable to use a combination of two or more kinds of charge generating materials having spectral sensitivity characteristics in different spectral regions of the visible region and the near red region. Among them, a disazo pigment, a trisazo pigment and a phthalocyanine pigment are preferably used in combination. More preferred.

  The binder resin used for the charge generation layer is not particularly limited, but examples include polyvinyl butyral resin, polyvinyl formal resin, polyvinyl acetal type such as partially acetalized polyvinyl butyral resin in which a part of butyral is modified with formal, acetal, or the like. Resin, Polyarylate resin, Polycarbonate resin, Polyester resin, Modified ether type polyester resin, Phenoxy resin, Polyvinyl chloride resin, Polyvinylidene chloride resin, Polyvinyl acetate resin, Polystyrene resin, Acrylic resin, Methacrylic resin, Polyacrylamide resin, Polyamide Resin, polyvinyl pyridine resin, cellulosic resin, polyurethane resin, epoxy resin, silicone resin, polyvinyl alcohol resin, polyvinyl pyrrolidone resin, casein, vinyl chloride -Vinyl acetate-vinyl acetate copolymers such as vinyl acetate copolymers, hydroxy-modified vinyl chloride-vinyl acetate copolymers, carboxyl-modified vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-maleic anhydride copolymers, etc. Insulating resins such as polymers, styrene-butadiene copolymers, vinylidene chloride-acrylonitrile copolymers, styrene-alkyd resins, silicon-alkyd resins, phenol-formaldehyde resins, poly-N-vinylcarbazole, polyvinyl anthracene, polyvinyl And organic photoconductive polymers such as perylene. Any one of these binder resins may be used alone, or two or more thereof may be mixed and used in any combination.

Specifically, the charge generation layer is prepared by, for example, preparing a coating solution by dispersing a charge generation material in a solution obtained by dissolving the above-described binder resin in an organic solvent, and providing this on a conductive support (providing an undercoat layer). In some cases, it is formed by coating (on the undercoat layer).
The solvent used for preparing the coating solution is not particularly limited as long as it dissolves the binder resin. For example, saturated aliphatic solvents such as pentane, hexane, octane, and nonane, and aromatics such as toluene, xylene, and anisole. Group solvents, halogenated aromatic solvents such as chlorobenzene, dichlorobenzene, chloronaphthalene, amide solvents such as N, N-dimethylformamide, N-methyl-2-pyrrolidone, methanol, ethanol, isopropanol, n-butanol, Alcohol solvents such as benzyl alcohol, aliphatic polyhydric alcohols such as glycerin and polyethylene glycol, chain or cyclic ketone solvents such as acetone, cyclohexanone and methyl ethyl ketone, ester systems such as methyl formate, ethyl acetate and n-butyl acetate Solvent, methyl chloride Halogenated hydrocarbon solvents such as ethylene, chloroform, 1,2-dichloroethane, chain or cyclic ether solvents such as diethyl ether, dimethoxyethane, tetrahydrofuran, 1,4-dioxane, methyl cellosolve, ethyl cellosolve, acetonitrile , Aprotic polar solvents such as dimethyl sulfoxide, sulfolane, hexamethylphosphoric triamide, n-butylamine, isopropanolamine, diethylamine, triethanolamine, nitrogen-containing compounds such as ethylenediamine, triethylenediamine, triethylamine, mineral oil such as ligroin, water Etc. Any one of these may be used alone, or two or more of these may be used in combination. In addition, when providing the above-mentioned undercoat layer, what does not melt | dissolve this undercoat layer is preferable.

  In the charge generation layer, the compounding ratio (mass) of the binder resin and the charge generation material is usually 10 parts by mass or more, preferably 30 parts by mass or more, and usually 1000 parts by mass with respect to 100 parts by mass of the binder resin. Part or less, preferably 500 parts by mass or less, and the film thickness is usually 0.1 μm or more, preferably 0.15 μm or more, and usually 10 μm or less, preferably 0.6 μm or less. If the ratio of the charge generation material is too high, the stability of the coating solution may be reduced due to aggregation of the charge generation material, while if the ratio of the charge generation material is too low, the sensitivity as a photoreceptor may be decreased. There is.

  As a method for dispersing the charge generation material, a known dispersion method such as a ball mill dispersion method, an attritor dispersion method, a sand mill dispersion method, or a bead mill dispersion can be used. At this time, it is effective to refine the particles to a particle size in the range of 0.5 μm or less, preferably 0.3 μm or less, more preferably 0.15 μm or less.

<Charge transport layer>
A single charge transport layer is formed on the charge generation layer, and the charge transport layer becomes the outermost surface layer. In this case, it is advantageous in terms of cost as compared with the case where the protective layer is provided, and since the number of layers is small, uniform charge transport is possible and the electrical characteristics are also advantageous. The charge transport layer contains a binder resin and a charge transport material, and contains 3 to 30 wt% of silica particles having an average primary particle size of 0.2 to 1 μm. You may contain another component as needed.

The hole mobility of the charge transport layer is 2.0 × 10 ⁻⁵ cm ² / V · s or more at an electric field strength of 2.0 × 10 ⁵ V / μm and an air temperature of 21 ° C. From the viewpoint of repeated electrical characteristics, the hole mobility of the charge transport layer is preferably 3.0 × 10 ⁻⁵ cm ² / V · s or more at an electric field strength of 2.0 × 10 ⁵ V / μm and an air temperature of 21 ° C. The mobility of the photoconductor at an electric field strength of 2.0 × 10 ⁵ V / μm and an air temperature of 21 ° C. is determined by TOF (Time-of-fli
ght) method.

Specifically, such a charge transport layer is obtained by, for example, preparing a coating liquid by dissolving or dispersing a charge transport material and the like, a binder resin, and a filler in a solvent, and coating and drying on the charge generation layer. be able to.
From the viewpoint of filming resistance, the average primary particle size of the silica particles is 0.2 μm or more, preferably 0.3 μm or more, and more preferably 0.4 μm or more. From the viewpoint of coating solution stability, it is 1 μm or less, preferably 0.9 μm or less, and more preferably 0.8 μm or less. When the average primary particle diameter of the silica particles is smaller than 0.2 μm, the effect of suppressing filming is small. When it is larger than 1 μm, the stability of the coating solution is deteriorated.

The lower limit of the content of the silica particles is 3 wt% or more of the entire charge transport layer, and preferably 5 wt% or more. The upper limit is 30 wt% or less of the entire charge transport layer, preferably 15 wt% or less, and more preferably 10 wt% or less. When the content of silica particles is less than 3 wt%, the effect of suppressing filming is small. When the amount is more than 30 wt%, the aggregation of the silica particles in the charge transport layer film becomes intense, so that the effect of suppressing filming is diminished and the dispersion stability of the coating solution is deteriorated.

  The silica particles are preferably surface-treated with a reactive organosilicon compound. The surface treatment can be produced by a dry method and a wet method. In the dry method, the surface treatment agent can be mixed with the metal oxide particles so that the metal oxide particles are coated, and heat treatment is performed as necessary. In the wet method, the metal oxide particles and a mixture of the surface treatment agent of the present invention mixed with an appropriate solvent are thoroughly stirred until they are uniformly attached or mixed with media, and then dried, if necessary. It can be manufactured by performing heat treatment.

  Examples of reactive organosilicon compounds include silane coupling agents, silane treatment agents, and siloxane compounds, with silane treatment agents being preferred. Among the silane treatment agents, silane treatment agents having an alkyl group having 1 to 3 carbon atoms are preferable. Such silane treating agents include hexamethyldisilazane, trimethylmethoxysilane, trimethylethoxysilane, trimethylchlorosilane, dimethyldichlorosilane, dimethyldimethoxysilane, dimethylethoxysilane, methyldimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane. Etc.

As a charge transport material, the hole mobility of the charge transport layer is set to an electric field strength of 2.0 × 10 ⁵ V / μm, and the temperature is 21 ° C.
In order to achieve 2.0 × 10 ⁻⁵ cm ² / Vs or more in the case, it is necessary to be a high-performance charge transport material.
For this purpose, the charge polarizability α of the charge transport material is usually α> 100 (Å ³ ), preferably α> 115 (Å ³ ), and more preferably α> 120 (Å ³ ). preferable.

The dipole moment of the charge transport material is usually P <1.60 (D), preferably P <1.55 (D), and more preferably P <1.50 (D).
In addition, as the values of the polarizability and the dipole moment, values calculated by the molecular orbital method may be used instead of the actually measured values. Specifically, when PM3 of MOPAC93 or AM1 parameter is used, the calculated value αcal of the polarizability α is usually the following formula αcal> 70 (Å ³ ) and αcal> 80 (Å ³ ). It is preferable.

The calculated value Pcal of the dipole moment using the above calculation method is normally Pcal <1.8 (D), preferably Pcal <1.6 (D), and preferably (D). More preferred.
As such a charge transport material, a carbazole derivative, an aromatic amine derivative, a stilbene derivative, a butadiene derivative, an enamine derivative, and a substance in which a plurality of these compounds are bonded is preferable. Any one of these charge transport materials may be used alone, or two or more thereof may be used in any combination.

The molecular weight of the charge transport material is usually 600 or more, preferably 650 or more from the viewpoint of charge transport ability, and usually 2000 or less, preferably 1200 or less from the viewpoint of solubility.
Specifically, compounds such as the following formulas (1) to (3) are preferably used. Compounds such as formula (1) or (3) are more preferred, and formula (1) is particularly preferred.

(Formula (1) Ar ^{1 to} Ar ⁵ each represents an aryl group which may have an independent substituent, and Ar ^{6 to} Ar ⁹ each represents an arylene group which may have an independent substituent. M and N each independently represent an integer of 1 to 3.
In the above formula (1), Ar ^{1 to} Ar ⁵ each independently represents an aryl group which may have a substituent, specifically a phenyl group, a naphthyl group, a biphenyl group, an anthryl group, a phenanthryl group, or the like. Is given. Among these, in consideration of the characteristics of the electrophotographic photoreceptor, a phenyl group and a naphthyl group are preferable. From the viewpoint of charge transport capability, a phenyl group and a naphthyl group are more preferable, and a phenyl group is further preferable. Examples of the substituent that Ar ^{1 to} Ar ⁵ may have include an alkyl group, an aryl group, an alkoxy group, and a halogen atom. Specifically, examples of the alkyl group include a methyl group, an ethyl group, and n-propyl. Groups, linear alkyl groups such as n-butyl group, branched alkyl groups such as isopropyl group and ethylhexyl group, and cyclic alkyl groups such as cyclohexyl group. The aryl group may have a substituent. Examples thereof include a phenyl group and a naphthyl group, and examples of the alkoxy group include linear alkoxy groups such as a methoxy group, an ethoxy group, an n-propoxy group, and an n-butoxy group, an isopropoxy group, and an ethylhexyloxy group. Cyclic alkoxy groups, cyclic alkoxy groups such as cyclohexyloxy group, trifluoromethoxy group, pentafluoroethoxy group, 1,1,1-trifluoro They include alkoxy groups having a fluorine atom such as Oroetokishi group, the halogen atom fluorine atom, chlorine atom, bromine atom and the like. Among these, an alkyl group having 1 to 20 carbon atoms and an alkoxy group having 1 to 20 carbon atoms are preferable from the versatility of production raw materials, and an alkyl group having 1 to 12 carbon atoms and carbon number from the viewpoint of handleability during production. An alkoxy group having 1 to 12 carbon atoms is more preferable, and an alkyl group having 1 to 6 carbon atoms and an alkoxy group having 1 to 6 carbon atoms are more preferable from the viewpoint of light attenuation characteristics as an electrophotographic photoreceptor. In the case where Ar ^{1 to} Ar ⁵ are phenyl groups, it is preferable to have a substituent from the viewpoint of charge transport ability, and the number of substituents can be 1 to 5, but from the versatility of manufacturing raw materials, 1 1 to 3 are preferable, and from the viewpoint of the characteristics of the electrophotographic photosensitive member, 1 to 2 are more preferable, and when Ar ^{1 to} Ar ⁵ are naphthyl groups, the number of substituents from the versatility of the production raw material Is preferably 2 or less or not having a substituent, and more preferably, the number of substituents is 1 or having no substituent.

In the above formula (1), Ar ^{6 to} Ar ⁹ each independently represent an arylene group which may have a substituent. Specifically, a phenylene group, a biphenylene group, a naphthylene group, an anthrylene group, or a phenanthrylene group Among them, a phenylene group and a naphthylene group are preferable, and a phenylene group is more preferable in consideration of the characteristics of the electrophotographic photosensitive member. Examples of the substituent that Ar ^{6 to} Ar ⁹ may have include an alkyl group, an aryl group, an alkoxy group, and a halogen atom. Specifically, examples of the alkyl group include a methyl group, an ethyl group, and n-propyl. Groups, linear alkyl groups such as n-butyl group, branched alkyl groups such as isopropyl group and ethylhexyl group, and cyclic alkyl groups such as cyclohexyl group. The aryl group may have a substituent. Examples thereof include a phenyl group and a naphthyl group, and examples of the alkoxy group include linear alkoxy groups such as a methoxy group, an ethoxy group, an n-propoxy group, and an n-butoxy group, an isopropoxy group, and an ethylhexyloxy group. Cyclic alkoxy groups, cyclic alkoxy groups such as cyclohexyloxy group, trifluoromethoxy group, pentafluoroethoxy group, 1,1,1-trifluoro They include alkoxy groups having a fluorine atom such as Oroetokishi group, the halogen atom fluorine atom, chlorine atom, bromine atom and the like. Among these, a C1-C6 alkyl group and a C1-C6 alkoxy group are preferable from the versatility of a manufacturing raw material, and a C1-C4 alkyl group and carbon number from the surface of the handling property at the time of manufacture 1-4 alkoxy groups are more preferable, and a methyl group, an ethyl group, a methoxy group, and an ethoxy group are more preferable from the viewpoint of light attenuation characteristics as an electrophotographic photosensitive member. When Ar ^{6 to} Ar ⁹ have a substituent, the molecular structure is twisted, and π-conjugate expansion in the molecule may be hindered, and the electron transport ability may be reduced. Therefore, Ar ^{6 to} Ar ⁹ may be substituted. In view of the characteristics of the electrophotographic photosensitive member, 1,3-phenylene group, 1,4-phenylene group, 1,4-naphthylene group, 2,6-naphthylene group, 2,8-naphthylene are preferable. A group is more preferable, and a 1,4-phenylene group is still more preferable.

  M and N each independently represent an integer of 1 to 3. Since the solubility in a coating solvent tends to decrease as M and N increase, it is preferably 2 or less, and more preferably 1 from the viewpoint of charge transport ability as a charge transport material. When M and N are 1, it represents an ethenyl group and has a geometric isomer, but a trans structure is preferable from the viewpoint of the characteristics of an electrophotographic photoreceptor. When M and N are 2, it represents a butadienyl group, which also has a geometric isomer, but a mixture of two or more geometric isomers is preferable from the viewpoint of coating solution storage stability. Moreover, the electrophotographic photoreceptor of the present invention may usually contain a compound represented by formula (1) as a single component in the photosensitive layer, or as a mixture of compounds represented by formula (1). It can also be contained.

(In Formula (2), R ^{1 to} R ⁵ each represent an independent hydrogen atom, alkyl group, aryl group, or alkoxy group. N represents an integer of 1 to 3, and k, l, o, and p are each represented by Independently represents an integer of 1 to 5, and m independently represents an integer of 1 to 4. Z represents a phenylene group which may have an alkyl group, an aryl group or an alkoxy group, or a single bond. R ^{6 to} R ⁷ represent a hydrogen atom or a phenyl group which may have an alkyl group.

In the above formula (2), R ¹ and R ² each independently represent a hydrogen atom, an alkyl group, an aryl group, or an alkoxy group. Specifically, examples of the alkyl group include a methyl group, an ethyl group, and n- Examples thereof include linear alkyl groups such as propyl group and n-butyl group, branched alkyl groups such as isopropyl group and ethylhexyl group, and cyclic alkyl groups such as cyclohexyl group. The aryl group has a substituent. Phenyl group, naphthyl group and the like may be mentioned, and as alkoxy group, straight chain alkoxy group such as methoxy group, ethoxy group, n-propoxy group, n-butoxy group, isopropoxy group, ethylhexyloxy group, etc. A branched alkyl group, and a cyclohexyloxy group. Among these, a hydrogen atom, a methyl group, an ethyl group, a methoxy group, and an ethoxy group are preferable from the viewpoints of versatility of production raw materials and charge transport ability as a charge transport material. The bonding position of each substituent with respect to the benzene ring can be usually any of the o-position, m-position and p-position with respect to the vinyl group, but from the viewpoint of ease of production, the o-position or p-position. Either of the positions is preferred.

In the above formula (2), R ^{3 to} R ⁵ each independently represents a hydrogen atom, an alkyl group, an aryl group, or an alkoxy group. Specifically, examples of the alkyl group include a methyl group, an ethyl group, and n -Linear alkyl groups such as propyl group and n-butyl group, branched alkyl groups such as isopropyl group and ethylhexyl group, and cyclic alkyl groups such as cyclohexyl group. The aryl group has a substituent. Phenyl group, naphthyl group, etc., which may be included, and as alkoxy group, linear alkoxy group such as methoxy group, ethoxy group, n-propoxy group, n-butoxy group, isopropoxy group, ethylhexyloxy group And branched alkyl groups such as cyclohexyloxy and the like. Among these, a hydrogen atom, a C1-C8 alkyl group, and a C1-C8 alkoxy group are preferable from the versatility of a manufacturing raw material, and a hydrogen atom and a C1-C6 from the surface of the handleability at the time of manufacture are preferable. More preferably, an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 2 carbon atoms from the viewpoint of light attenuation characteristics as an electrophotographic photosensitive member, and a charge as a charge transport material. From the viewpoint of transport ability, a hydrogen atom is particularly preferable.

In the above formula (2), Z represents an alkyl group, an aryl group, a phenylene group which may have an alkoxy group or a single bond. Specifically, examples of the alkyl group include a methyl group, an ethyl group, n A linear alkyl group such as -propyl group and n-butyl group, a branched alkyl group such as isopropyl group and ethylhexyl group, and a cyclic alkyl group such as cyclohexyl group,
Examples of the aryl group include an optionally substituted phenyl group and naphthyl group. Examples of the alkoxy group include linear alkoxy groups such as a methoxy group, an ethoxy group, an n-propoxy group, and an n-butoxy group. Group, branched alkyl groups such as isopropoxy group and ethylhexyloxy group, and cyclohexyloxy group. Among these, a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, and an alkoxy group having 1 to 8 carbon atoms are preferable from the viewpoint of versatility of production raw materials, and a hydrogen atom and carbon number of 1 from the viewpoint of handling at the time of manufacture. More preferable are an alkyl group having 1 to 6 carbon atoms and an alkoxy group having 1 to 6 carbon atoms. From the viewpoint of light attenuation characteristics as an electrophotographic photoreceptor, an alkyl group having 1 to 4 carbon atoms and an alkoxy group having 1 to 4 carbon atoms are preferable. Further, an alkyl group having 1 to 4 carbon atoms is particularly preferable from the viewpoint of resistance to ozone of the electrophotographic photosensitive member, and a methyl group and an ethyl group are most preferable from the viewpoint of charge transport ability as a charge transport material. Further, when R ^{6 to} R ⁷ are a methyl group or an ethyl group, the bonding position of each substituent to the benzene ring can be any of the o-position, m-position and p-position with respect to the styryl group. However, from the viewpoint of ease of production, either the o-position or the p-position is preferable. When the total of alkyl groups such as methyl group and ethyl group for one benzene ring is 2 or more, it is preferably substituted at either o-position or p-position, from the viewpoint of electrophotographic photoreceptor characteristics, More preferably, the total number of alkyl groups is 2, and the two substituents are more preferably substituted at the p-position and o-position, respectively, or both are further substituted at the o-position.

In the above formula (2), examples of the alkyl group in the case where A is a phenyl group optionally having an alkyl group include those described above.
k, l, o, and p are each independently an integer of 1 to 5, and m is independently an integer of 1 to 4. k, l, m, o, when p represents an integer of 2 or more, may be different plurality of R ¹ to R ⁴ bonded to the benzene ring, respectively, also, a plurality of R ¹ ~ bonded to the benzene ring R ⁴ may also be different from each other.

n represents an integer of 1 to 3. When n increases, the solubility in the coating solvent tends to decrease, preferably 1 or 2, and more preferably 2 from the viewpoint of charge transport ability as a charge transport material.
The arylene group portion to which the diphenylamino group is bonded represents a phenylene group when n = 1, a biphenylene group when n = 2, or a terphenylene group when n = 3. The position at which the two diphenylamino groups are bonded to the arylene group is not limited as long as the effect of the present invention is not significantly impaired. However, when n = 1, the two diphenylamino groups have two diphenylamino groups from the viewpoint of the chargeability of the electrophotographic photosensitive member. It is preferable that the m-position relationship is established at the bonding position of the phenylene group. In the case of n = 2, from the viewpoint of charge transport ability as a charge transport material, the position where the diphenylamino group is bonded to the biphenylene group is preferably bonded to the 4th and 4 ′ positions of the biphenylene group, and n = 3 In this case, a p-terphenylene group is preferable among the terphenylene groups because of the versatility of the raw materials for production, and the bonding position of the diphenylamine group to the p-terphenylene group is the 4-position and the 4-position from the viewpoint of charge transport ability as a charge transport material. Bonding at the '' position is preferred.

In addition, the electrophotographic photoreceptor of the present invention may usually contain a compound represented by the formula (2) as a single component in the photosensitive layer, or a compound having a different structure represented by the formula (2). You may contain as a mixture of these. As the mixture, when a plurality of so-called positional isomers in the structure represented by the formula (2) are different only in the substitution positions of R ^{1 to} R ⁵ , their electronic states are close to each other and the charge transport trap In addition to being difficult to become, it is preferable from the viewpoint of suppressing crystal formation in the coating solution or film. As the positional isomers, it is more preferable to use a mixture of R ¹ and R ² having different substitution positions from the viewpoint of ease of synthesis of the compound, and the substitution positions of R ¹ and R ² are in the o position. , P-position is most preferably used in combination.

(In Formula (3), R ^{8 to} R ¹² each represent an independent hydrogen atom, alkyl group, aryl group, or alkoxy group. S, t, and u each represent an integer of 1 to 5, and v and w are respectively Represents an integer of 1 or more and 4 or less.)

In the above formula (3), R ⁸ represents any one of a hydrogen atom, an alkyl group, an aryl group, and an alkoxy group. Specifically, examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an n- Examples include linear alkyl groups such as butyl groups, branched alkyl groups such as isopropyl groups and ethylhexyl groups, and cyclic alkyl groups such as cyclohexyl groups, and aryl groups include phenyl groups that may have a substituent. , A naphthyl group, etc., and the alkoxy group includes a linear alkyl group such as a methoxy group, an ethoxy group, an n-propoxy group and an n-butoxy group, a branched alkyl group such as an isopropoxy group and an ethylhexyloxy group. And a cyclohexyloxy group. Among these, a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, and an alkoxy group having 1 to 8 carbon atoms are preferable from the viewpoint of versatility of production raw materials, and a hydrogen atom and carbon number of 1 from the viewpoint of handling at the time of manufacture. More preferable are an alkyl group having 1 to 6 carbon atoms and an alkoxy group having 1 to 6 carbon atoms. From the viewpoint of light attenuation characteristics as an electrophotographic photoreceptor, an alkyl group having 1 to 4 carbon atoms and an alkoxy group having 1 to 4 carbon atoms are preferable. Further, an alkyl group having 1 to 4 carbon atoms is particularly preferable from the viewpoint of resistance to ozone of the electrophotographic photosensitive member, and a linear or branched alkyl group having 3 to 4 carbon atoms is most preferable from the viewpoint of solubility. Furthermore, when R ⁸ is an alkyl group, the substituent can be bonded to the benzene ring at any position of the o-position, m-position or p-position with respect to the styryl group. In view of the above, the o-position and / or the p-position are preferable.

In the above formula (3), R ⁹ and R ¹⁰ each independently represent a hydrogen atom, an alkyl group, an aryl group, or an alkoxy group. Specifically, examples of the alkyl group include a methyl group, an ethyl group, and n -Linear alkyl groups such as propyl group and n-butyl group, branched alkyl groups such as isopropyl group and ethylhexyl group, and cyclic alkyl groups such as cyclohexyl group. The aryl group has a substituent. Phenyl group, naphthyl group, etc., which may be included, and as alkoxy group, linear alkoxy group such as methoxy group, ethoxy group, n-propoxy group, n-butoxy group, isopropoxy group, ethylhexyloxy group And branched alkyl groups such as cyclohexyloxy and the like. Among these, a hydrogen atom, a C1-C8 alkyl group, and a C1-C8 alkoxy group are preferable from the versatility of a manufacturing raw material, and a hydrogen atom and a C1-C6 from the surface of the handleability at the time of manufacture are preferable. More preferably, an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 2 carbon atoms from the viewpoint of light attenuation characteristics as an electrophotographic photosensitive member, and a charge as a charge transport material. From the viewpoint of transport ability, a hydrogen atom is particularly preferable.

In the above formula (3), R ¹¹ and R ¹² each independently represent a hydrogen atom, an alkyl group, an aryl group, or an alkoxy group. Specifically, examples of the alkyl group include a methyl group, an ethyl group, and n- Examples thereof include linear alkyl groups such as propyl group and n-butyl group, branched alkyl groups such as isopropyl group and ethylhexyl group, and cyclic alkyl groups such as cyclohexyl group. The aryl group has a substituent. Phenyl group, naphthyl group and the like may be mentioned, and as alkoxy group, straight chain alkoxy group such as methoxy group, ethoxy group, n-propoxy group, n-butoxy group, isopropoxy group, ethylhexyloxy group, etc. A branched alkyl group, and a cyclohexyloxy group. Among these, a hydrogen atom, a methyl group, an ethyl group, a methoxy group, and an ethoxy group are preferable from the viewpoints of versatility of production raw materials and charge transport ability as a charge transport material. The bonding position of each substituent to the benzene ring can be usually any of the o-position, m-position and p-position with respect to the styryl group, but from the viewpoint of ease of production, the o-position or p-position. Any of the positions is preferred.

  The structure of the charge transport material suitable for the present invention is exemplified below. The following structures are illustrated to make the present invention more concrete, and are not limited to the following structures unless departing from the concept of the present invention.

  The charge transport layer is formed in such a form that these charge transport materials are bound to the binder resin. Examples of the binder resin used for the charge transport layer include vinyl polymers such as polymethyl methacrylate, polystyrene, and polyvinyl chloride, and copolymers thereof, polycarbonate, polyarylate, polyester, polyester carbonate, polysulfone, polyimide, phenoxy, Examples thereof include epoxies and silicone resins, and these partially crosslinked cured products can also be used. Of the binder resins, polycarbonate resins and polyarylate resins are particularly preferable. These resins may be used alone or in combination.

  Specific examples of suitable structures of the binder resin are shown below. These specific examples are shown for illustration, and any known binder resin may be mixed and used as long as it does not contradict the gist of the present invention.

  The ratio between the binder resin and the charge transport material is preferably 30 parts by mass or more with respect to 100 parts by mass of the binder resin from the viewpoint of stability and charge mobility when the charge transport material is repeatedly used. 40 parts by mass or more is more preferable. On the other hand, from the viewpoints of thermal stability and abrasion resistance of the photosensitive layer, it is preferable to use the charge transport material in a ratio of usually 150 parts by mass or less. Especially, 120 mass parts or less are more preferable from a compatible viewpoint of charge transport material and binder resin, and 60 mass parts or less are especially preferable.

  The lower limit of the viscosity average molecular weight (Mv) is usually 10,000 or more, preferably 20,000 or more, more preferably 30,000 or more, and the upper limit is usually 300,000 or less, preferably 200,000 or less. More preferably, it is 80,000 or less. When the viscosity average molecular weight (Mv) is excessively small, the mechanical strength when obtained as a film for forming a photoconductor tends to decrease. In addition, when the viscosity average molecular weight (Mv) is excessively large, the viscosity as a coating solution increases, and it tends to be difficult to apply a suitable film thickness, and the dispersibility of silica particles may be deteriorated. There is.

The thickness of the charge transport layer is not particularly limited, but from the viewpoint of electrical characteristics and image stability, and further from the viewpoint of high resolution, it is usually preferably 5 μm or more and 50 μm or less, more preferably 10 μm or more and 35 μm or less, and still more preferably. 15 μm or more and 25 μm or less.
In order to improve the film forming property, flexibility, coating property, stain resistance, gas resistance, light resistance, etc. in the charge transport layer, or to further improve the mechanical strength of the photosensitive layer, a known plasticizer, It is also preferable to add additives such as a lubricant, a dispersion aid, an antioxidant, an ultraviolet absorber, an electron-withdrawing compound, a dye, a pigment, a sensitizer, a leveling agent, a stabilizer, a fluidity-imparting agent, and a crosslinking agent. . Examples of the antioxidant include hindered phenol compounds and hindered amine compounds. Examples of dyes and pigments include various pigment compounds and azo compounds. Examples of leveling agents include silicone oil and fluorine-based surfactants.

Electron-withdrawing compounds include tetracyanoquinodimethane, dicyanoquinomethane, cyano compounds such as aromatic esters having a dicyanoquinovinyl group, nitro compounds such as 2,4,6-trinitrofluorenone, and condensation of perylene. Polycyclic aromatic compounds, diphenoquinone derivatives, quinones, aldehydes, ketones, esters, acid anhydrides, phthalides, metal complexes of substituted and unsubstituted salicylic acid, metal salts of substituted and unsubstituted salicylic acid, aromatic carboxylic acids And metal salts of aromatic carboxylic acids. Preferably, cyanide compounds, nitro compounds, condensed polycyclic aromatic compounds, diphenoquinone derivatives, metal complexes of substituted and unsubstituted salicylic acid, metal salts of substituted and unsubstituted salicylic acid, metal complexes of aromatic carboxylic acid, aromatic carboxylic acid Metal salt is used <Method for forming each layer>
Each layer constituting the photoreceptor is formed by immersing, coating, spraying, nozzle coating, bar coating, roll coating, blade coating, etc., on a support, a coating solution obtained by dissolving or dispersing a substance contained in each layer in a solvent. In this method, the coating and drying steps are sequentially repeated for each layer.

  Although there is no particular limitation on the solvent or dispersion medium used for the production of the photosensitive layer, specific examples include ethers such as tetrahydrofuran, 1,4-dioxane and dimethoxyethane, esters such as methyl formate and ethyl acetate, acetone, Ketones such as methyl ethyl ketone and cyclohexanone, aromatic hydrocarbons such as benzene, toluene and xylene, dichloromethane, chloroform, 1,2-dichloroethane, 1,1,2-trichloroethane, 1,1,1-trichloroethane, tetrachloroethane, Chlorinated hydrocarbons such as 1,2-dichloropropane and trichloroethylene, nitrogen-containing compounds such as n-butylamine, isopropanolamine, diethylamine, triethanolamine, ethylenediamine, and triethylenediamine, acetonitrile, N-methylpyrrole Emissions, N, N- dimethylformamide, aprotic polar solvents such as dimethyl sulfoxide and the like. Moreover, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and kinds.

The amount of the solvent or the dispersion medium used is not particularly limited, but considering the purpose of each layer and the properties of the selected solvent / dispersion medium, it is appropriately determined so that the physical properties such as the solid content concentration and viscosity of the coating liquid are within a desired range. It is preferable to adjust.
In the case of the charge transport layer, the solid content concentration of the coating solution is usually 5% by mass or more, preferably 10% by mass or more, and usually 40% by mass or less, preferably 35% by mass or less. Further, the viscosity of the coating solution is usually in the range of 10 cps or more, preferably 50 cps or more, and usually 500 cps or less, preferably 400 cps or less.

In the case of the charge generation layer, the solid content concentration of the coating solution is usually 0.1% by mass or more, preferably 1% by mass or more, and usually 15% by mass or less, preferably 10% by mass or less. The viscosity of the coating solution is usually 0.01 cps or more, preferably 0.1 cps or more, and usually 20 cps or less, preferably 10 cps or less.
Examples of the coating method include a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a wire bar coating method, a blade coating method, a roller coating method, an air knife coating method, and a curtain coating method. Other known coating methods can also be used.

<Image forming apparatus>
An image forming apparatus such as a copying machine or a printer using the electrophotographic photosensitive member of the present invention includes at least charging, exposure, development, transfer, and cleaning processes. Also good.
As the charging method (charging machine), for example, in addition to corotron and scorotron charging using corona discharge, a direct charging means for charging a surface by contacting a directly charged member to which a voltage is applied may be used. As the direct charging means, any one such as contact charging using a conductive roller, brush, or film may be used, and any of those that involve air discharge or injection charging that does not involve air discharge is possible. Among these, scorotron charging is preferable in the charging method using corona discharge in order to keep the dark portion potential constant. As a charging method in the case of a contact charging device using a conductive roller or the like, DC charging or AC superimposed DC charging can be used.

  As the exposure light, halogen lamps, fluorescent lamps, lasers (semiconductors, He—Ne), LEDs, photoconductor internal exposure systems, and the like are used. As digital electrophotographic systems, lasers, LEDs, optical shutter arrays, and the like are used. preferable. As the wavelength, in addition to monochromatic light of 780 nm, monochromatic light near a short wavelength in the 600 to 700 nm region and short wavelength monochromatic light in the 380 to 500 nm region can be used.

As the toner, in addition to the pulverized toner, a polymerized toner such as suspension polymerization or emulsion polymerization aggregation method can be used. In particular, in the case of the polymerized toner, those having a small particle diameter of about 4 to 8 μm in average diameter are used, and those having a shape close to a spherical shape or those outside a potato-like spherical shape can be used. The polymerized toner is excellent in charging uniformity and transferability and is suitably used for high image quality.
For the transfer step, electrostatic transfer methods such as corona transfer, roller transfer, and belt transfer, pressure transfer methods, and adhesive transfer methods are used. For fixing, heat roller fixing, flash fixing, oven fixing, pressure fixing, or the like is used.

For cleaning, brush cleaner, magnetic brush cleaner, electrostatic brush cleaner, magnetic roller cleaner, blade cleaner, etc. are used.
In many cases, the static elimination step is omitted, but when used, a fluorescent lamp, LED, or the like is used, and an exposure energy that is three times or more of the exposure light is often used as the intensity. In addition to these processes, a pre-exposure process and an auxiliary charging process may be included.

An embodiment of an image forming apparatus using the electrophotographic photosensitive member of the present invention will be described with reference to FIG. However, the embodiment is not limited to the following description, and can be arbitrarily modified without departing from the gist of the present invention.
As shown in FIG. 1, the image forming apparatus includes an electrophotographic photosensitive member 1, a charging device 2, an exposure device 3, and a developing device 4, and further, a transfer device 5, a cleaning device 6 and a fixing device as necessary. A device 7 is provided.

The electrophotographic photoreceptor 1 is not particularly limited as long as it is the above-described electrophotographic photoreceptor of the present invention, but in FIG. 1, as an example, a drum in which the above-described photosensitive layer is formed on the surface of a cylindrical conductive support. The photoconductor is shown. A charging device 2, an exposure device 3, a developing device 4, a transfer device 5, and a cleaning device 6 are disposed along the outer peripheral surface of the electrophotographic photosensitive member 1.
The charging device 2 charges the electrophotographic photosensitive member 1 and uniformly charges the surface of the electrophotographic photosensitive member 1 to a predetermined potential. In FIG. 1, a roller-type charging device (charging roller) is shown as an example of the charging device 2, but other corona charging devices such as corotron and scorotron, and contact-type charging devices such as charging brushes are often used.

  In many cases, the electrophotographic photosensitive member 1 and the charging device 2 are designed to be removable from the main body of the image forming apparatus as a cartridge including both of them (hereinafter also referred to as a photosensitive cartridge). For example, when the electrophotographic photoreceptor 1 or the charging device 2 deteriorates, the photoreceptor cartridge can be removed from the image forming apparatus main body, and another new photosensitive cartridge can be mounted on the image forming apparatus main body. ing. Also, the toner described later is often stored in the toner cartridge and designed to be removable from the main body of the image forming apparatus. When the toner in the used toner cartridge runs out, this toner cartridge is removed. It can be removed from the main body of the image forming apparatus and another new toner cartridge can be mounted. Further, a cartridge equipped with all of the electrophotographic photosensitive member 1, the charging device 2, and the toner may be used.

  The type of the exposure apparatus 3 is not particularly limited as long as it can expose the electrophotographic photoreceptor 1 to form an electrostatic latent image on the photosensitive surface of the electrophotographic photoreceptor 1. Specific examples include halogen lamps, fluorescent lamps, lasers such as semiconductor lasers and He—Ne lasers, LEDs, and the like. Further, exposure may be performed by a photoreceptor internal exposure method. The light used for the exposure is arbitrary. For example, the exposure may be performed using monochromatic light with a wavelength of 780 nm, monochromatic light with a wavelength slightly shorter than 600 nm to 700 nm, or monochromatic light with a short wavelength of 380 nm to 500 nm. .

  The type of the developing device 4 is not particularly limited, and an arbitrary device such as a dry development method such as cascade development, one-component conductive toner development, two-component magnetic brush development, or a wet development method can be used. In FIG. 1, the developing device 4 includes a developing tank 41, an agitator 42, a supply roller 43, a developing roller 44, and a regulating member 45, and has a configuration in which toner T is stored inside the developing tank 41. . Further, a replenishing device (not shown) for replenishing the toner T may be attached to the developing device 4 as necessary. The replenishing device is configured to be able to replenish toner T from a container such as a bottle or a cartridge.

The supply roller 43 is formed from a conductive sponge or the like. The developing roller 44 is made of a metal roll such as iron, stainless steel, aluminum, or nickel, or a resin roll obtained by coating such a metal roll with a silicon resin, a urethane resin, a fluorine resin, or the like. The surface of the developing roller 44 may be smoothed or roughened as necessary.
The developing roller 44 is disposed between the electrophotographic photoreceptor 1 and the supply roller 43 and is in contact with the electrophotographic photoreceptor 1 and the supply roller 43, respectively. The supply roller 43 and the developing roller 44 are rotated by a rotation drive mechanism (not shown). The supply roller 43 carries the stored toner T and supplies it to the developing roller 44. The developing roller 44 carries the toner T supplied by the supply roller 43 and contacts the surface of the electrophotographic photosensitive member 1.

  The regulating member 45 is formed of a resin blade such as silicon resin or urethane resin, a metal blade such as stainless steel, aluminum, copper, brass, phosphor bronze, or a blade obtained by coating such a metal blade with resin. The regulating member 45 contacts the developing roller 44 and is pressed against the developing roller 44 side with a predetermined force by a spring or the like (a general blade linear pressure is 5 to 500 g / cm). If necessary, the regulating member 45 may be provided with a function of imparting charging to the toner T by frictional charging with the toner T.

The agitator 42 is rotated by a rotation driving mechanism, and agitates the toner T and conveys the toner T to the supply roller 43 side. A plurality of agitators 42 may be provided with different blade shapes and sizes.
The type of the toner T is arbitrary, and in addition to the powdery toner, a polymerized toner using a suspension polymerization method, an emulsion polymerization method, or the like can be used. In particular, when a polymerized toner is used, a toner having a small particle diameter of about 4 to 8 μm is preferable, and the toner particles are used in various shapes ranging from a nearly spherical shape to a shape outside the spherical shape on the potato. be able to. The polymerized toner is excellent in charging uniformity and transferability and is suitably used for high image quality.

  The type of the transfer device 5 is not particularly limited, and an apparatus using an arbitrary system such as an electrostatic transfer method such as corona transfer, roller transfer, or belt transfer, a pressure transfer method, or an adhesive transfer method can be used. . Here, it is assumed that the transfer device 5 includes a transfer charger, a transfer roller, a transfer belt, and the like that are disposed to face the electrophotographic photoreceptor 1. The transfer device 5 applies a predetermined voltage value (transfer voltage) having a polarity opposite to the charging potential of the toner T, and transfers the toner image formed on the electrophotographic photosensitive member 1 to a recording paper (paper, medium) P. Is.

  The cleaning device 6 is not particularly limited, and any cleaning device such as a brush cleaner, a magnetic brush cleaner, an electrostatic brush cleaner, a magnetic roller cleaner, or a blade cleaner can be used. However, the present invention is effective for a blade cleaner. Is easy to demonstrate. The cleaning device 6 is for scraping off residual toner adhering to the photoreceptor 1 with a cleaning member and collecting the residual toner.

  The fixing device 7 includes an upper fixing member (fixing roller) 71 and a lower fixing member (fixing roller) 72, and a heating device 73 is provided inside the fixing member 71 or 72. FIG. 1 shows an example in which a heating device 73 is provided inside the upper fixing member 71. The upper and lower fixing members 71 and 72 include a fixing roll in which a metal base tube made of stainless steel, aluminum or the like is coated with silicon rubber, a fixing roll in which Teflon (registered trademark) resin is coated, a fixing sheet, or the like. A member can be used. Further, the fixing members 71 and 72 may be configured to supply a release agent such as silicone oil in order to improve the releasability, or may be configured to forcibly apply pressure to each other by a spring or the like.

  When the toner transferred onto the recording paper P passes between the upper fixing member 71 and the lower fixing member 72 heated to a predetermined temperature, the toner is heated to a molten state and cooled after passing through the recording paper. Toner is fixed on P. The type of the fixing device is not particularly limited, and a fixing device of any type such as heat roller fixing, flash fixing, oven fixing, pressure fixing, etc. can be provided including those used here.

In the electrophotographic apparatus configured as described above, an image is recorded as follows. That is, first, the surface (photosensitive surface) of the photoreceptor 1 is charged to a predetermined potential (for example, −600 V) by the charging device 2. At this time, charging may be performed by a DC voltage, or charging may be performed by superimposing an AC voltage on the DC voltage.
Subsequently, the photosensitive surface of the charged photoreceptor 1 is exposed by the exposure device 3 according to the image to be recorded, and an electrostatic latent image is formed on the photosensitive surface. The developing device 4 develops the electrostatic latent image formed on the photosensitive surface of the photoreceptor 1.

The developing device 4 thins the toner T supplied by the supply roller 43 with a regulating member (developing blade) 45 and has a predetermined polarity (here, the same polarity as the charging potential of the photosensitive member 1) and the negative polarity. ), And conveyed while being carried on the developing roller 44 to be brought into contact with the surface of the photoreceptor 1.
When the charged toner T carried on the developing roller 44 comes into contact with the surface of the photoreceptor 1, a toner image corresponding to the electrostatic latent image is formed on the photosensitive surface of the photoreceptor 1. This toner image is transferred onto the recording paper P by the transfer device 5. Thereafter, the toner remaining on the photosensitive surface of the photoreceptor 1 without being transferred is removed by the cleaning device 6.

After the transfer of the toner image onto the recording paper P, the final image is obtained by passing the fixing device 7 and thermally fixing the toner image onto the recording paper P.
In addition to the above-described configuration, the image forming apparatus may be configured to perform, for example, a static elimination process. The neutralization step is a step of neutralizing the electrophotographic photosensitive member by exposing the electrophotographic photosensitive member, and a fluorescent lamp, an LED, or the like is used as the neutralizing device. In addition, the light used in the static elimination process is often light having an exposure energy that is at least three times that of the exposure light.

  The image forming apparatus may be further modified. For example, the image forming apparatus may be configured to perform processes such as a pre-exposure process and an auxiliary charging process, may be configured to perform offset printing, and may be configured with a plurality of types. A full-color tandem system configuration using toner may be used.

<Manufacture of dispersion for undercoat layer coating formation>
・ Dispersion P1
A rutile type white titanium oxide (product name: TTO55N, manufactured by Ishihara Sangyo Co., Ltd.) treated with 3% methyldimethoxysilane and having an average primary particle size of 40 nm is ball milled in a methanol solvent for 5 hours to obtain a titanium oxide dispersed slurry. It was.

  The titanium oxide dispersion slurry, methanol / 1-propanol / toluene mixed solvent, and ε-caprolactam [compound represented by the following formula (A)] / bis (4-amino-3-methylcyclohexyl) methane [following formula Compound represented by (B)] / hexamethylenediamine [compound represented by the following formula (C)] / decamethylene dicarboxylic acid [compound represented by the following formula (D)] / octadecamethylene dicarboxylic acid [following formula (E The composition is represented by the following formula :), and the pellets of the copolymerized polyamide resin having a composition molar ratio of 60 mol% / 15 mol% / 5 mol% / 15 mol% / 5 ml% are stirred and mixed while heating to dissolve the polyamide pellets. Then, ultrasonic dispersion treatment was performed for 1 hour, and a PTFE membrane filter with a pore size of 5 μm (Advantech's Mytec LC), and the mass ratio of titanium oxide / copolymerized polyamide is 3/1, and the mass ratio of the mixed solvent of methanol / 1-propanol / toluene is 7/1/2. The undercoat layer forming coating solution P1 having a concentration of 18.0% by mass was obtained.

<Manufacture of dispersion for forming charge transport layer coating solution>
・ Dispersion P2
Bisphenol Z-type polycarbonate resin, charge transport material represented by the following structural formula (2), antioxidant Irg1076 manufactured by BASF, 2,4,5-trichlorobenzenesulfonsan 4- (2.2-dicyanoethenyl) phenyl ester (Acceptor) is dissolved in a mixed solvent of tetrahydrofuran: toluene = 8/2 by heating and stirring, and the mass ratio of binder resin / charge transport material / antioxidant / acceptor is 100/43/8 / 0.067. Thus, a charge transport layer forming coating solution P2 having a tetrahydrofuran / toluene mass ratio of 8/2 and a solid content concentration of 23.0% by mass was obtained.

・ Dispersion P3
Bisphenol Z-type polycarbonate resin, charge transport material represented by the above structural formula (2), antioxidant Irg1076 manufactured by BASF, and 2,4,5-trichlorobenzenesulfonsan 4- (2.2-dicyanoethenyl) phenyl The ester (acceptor) is dissolved by heating and stirring with a mixed solvent of tetrahydrofuran: toluene = 8/2, and the mass ratio of binder resin / charge transporting material / antioxidant is 100/80/8 / 0.067. A charge transport layer forming coating solution P3 having a mass ratio of / toluene of 8/2 and a solid content concentration of 23.0% by mass was obtained.

・ Dispersion P4
Silicon oxide slurry with an average primary particle size of 0.8μ surface-treated with hexamethylene disilazane (Nihon Shokubai Co., Ltd., product name KE-S100 surface treatment) was ultrasonically dispersed in a tetrahydrofuran solvent for 4 hours. Got. The silicon oxide slurry and the bisphenol Z-type polycarbonate resin, the charge transport material represented by the structural formula (2), the antioxidant Irg1076 manufactured by BASF, and 2,4,5-trichlorobenzenesulfonesan 4- (2 .2-dicyanoethenyl) phenyl ester (acceptor) is dissolved by heating with stirring in a tetrahydrofuran solvent, and the mass ratio of binder resin / charge transport material / silicon oxide / antioxidant / acceptor is 100/43/25/8 / 0.0. A charge transport layer forming coating solution P4 having a solid content of 24.0% by mass was obtained.

・ Dispersion P5
Silicon oxide slurry with an average primary particle size of 0.8μ surface-treated with hexamethylene disilazane (Nihon Shokubai Co., Ltd., product name KE-S100 surface treatment) was ultrasonically dispersed in a tetrahydrofuran solvent for 4 hours. Got. The silicon oxide slurry and the bisphenol Z-type polycarbonate resin, the charge transport material represented by the structural formula (2), the antioxidant Irg1076 manufactured by BASF, and 2,4,5-trichlorobenzenesulfonesan 4- (2 .2-dicyanoethenyl) phenyl ester (acceptor) is dissolved by heating and stirring in a tetrahydrofuran solvent, and the mass ratio of binder resin / charge transport material / silicon oxide / antioxidant / acceptor is 100/80/25/8 / 0.0. A charge transport layer forming coating solution P5 having a solid content of 24.0% by mass was obtained.

・ Dispersion P6
Silicon oxide slurry with an average primary particle size of 0.8μ surface-treated with hexamethylene disilazane (Nihon Shokubai Co., Ltd., product name KE-S100 surface treatment) was ultrasonically dispersed in a tetrahydrofuran solvent for 4 hours. Got. The silicon oxide slurry and bisphenol Z-type polycarbonate resin, the charge transport material represented by the structural formula (2), the antioxidant Irg1076 manufactured by BASF, and 2,4,5-trichlorobenzenesulfonesan 4- (2 .2-
Dicyanoethenyl) phenyl ester (acceptor) is dissolved by stirring with a tetrahydrofuran solvent, and the mass ratio of binder resin / charge transport material / silicon oxide / antioxidant / acceptor is 100/80 / 12.5 / 8 / 0.067. Thus, a charge transport layer forming coating solution P6 having a solid content concentration of 24.0% by mass was obtained.

・ Dispersion P7
Silicon oxide slurry with an average primary particle size of 0.8μ surface-treated with hexamethylene disilazane (Nihon Shokubai Co., Ltd., product name KE-S100 surface treatment) was ultrasonically dispersed in a tetrahydrofuran solvent for 4 hours. Got. The silicon oxide slurry and bisphenol Z-type polycarbonate resin, the charge transport material represented by the structural formula (2), the antioxidant Irg1076 manufactured by BASF, and 2,4,5-trichlorobenzenesulfonesan 4- (2 .2-
Dicyanoethenyl) phenyl ester (acceptor) is dissolved by heating and stirring with a tetrahydrofuran solvent, and the mass ratio of binder resin / charge transport material / silicon oxide / antioxidant / acceptor is 100/80/6/8 / 0.067. A charge transport layer forming coating solution P6 having a solid content concentration of 24.0% by mass was obtained.

・ Dispersion P8
Silicon oxide slurry having an average primary particle diameter of 16 nm (manufactured by Nippon Aerosil Co., Ltd., product name R972) was ultrasonically dispersed in a tetrahydrofuran solvent for 4 hours to obtain a silicon oxide slurry. The silicon oxide slurry and bisphenol Z-type polycarbonate resin, the charge transport material represented by the structural formula (2), the antioxidant Irg1076 manufactured by BASF, and 2,4,5-trichlorobenzenesulfonesan 4- (2 .2-dicyanoethenyl) phenyl ester (acceptor) is dissolved by heating and stirring with a tetrahydrofuran solvent, and the binder resin / charge transporting material / silicon oxide / antioxidant / acceptor are in a mass ratio of 100/43/15/8 / acceptor. In addition, a coating liquid P8 for forming a charge transport layer having a solid content concentration of 24.0% by mass was obtained.
[Example 1]
Dispersion P1 was prepared by cutting the surface to an outer diameter of 30 mm, a length of 340 mm, and a wall thickness of 1.0.
An undercoating layer was provided so as to have a dry film thickness of 1.25 μm.

Next, 10 parts of oxytitanium phthalocyanine showing a characteristic peak at a Bragg angle (2θ ± 0.2 °) of 27.3 ° in a powder X-ray spectrum pattern by CuKα ray, and polyvinyl butyral (Electrochemical Co., Ltd.) ), Product name # 6000C) 5 parts and 1,2-dimethoxyethane 500 parts were mixed, and pulverized and dispersed in a sand grind mill. The dispersion obtained by this dispersion treatment was dip coated on the undercoat layer of the previous aluminum cylinder, and a charge generation layer was provided so that the dry film thickness was 0.35 g / m ² .

Next, the dispersion P5 was dip-coated on the charge generation layer, air-dried and then heat-dried at 125 ° C., and a charge transport layer was provided so that the film thickness after drying was 25 μm.
The photoreceptor thus obtained is designated Q1.
[Example 2]
A drum produced in the same manner as the photoreceptor Q1 except that the dispersion P6 is applied to the charge transport layer by 25 μm is designated as the photoreceptor Q2.

[Example 3]
A drum manufactured in the same manner as the photoreceptor Q1 except that the dispersion P7 is applied to the charge transport layer by 25 μm is referred to as a photoreceptor Q3.
[Comparative Example 1]
A drum produced in the same manner as the photoreceptor Q1 except that the dispersion P2 is applied to the charge transport layer by 25 μm is designated as a photoreceptor Q4.

[Comparative Example 2]
A drum produced in the same manner as the photoconductor Q1 except that the dispersion P3 is applied to the charge transport layer by 25 μm is defined as a photoconductor Q5.
[Comparative Example 3]
A drum produced in the same manner as the photoconductor Q1 except that the dispersion P4 is applied to the charge transport layer by 25 μm is defined as a photoconductor Q6.

[Comparative Example 4]
A drum produced in the same manner as the photoreceptor Q1 except that the dispersion P8 is applied to the charge transport layer by 30 μm is designated as a photoreceptor Q7.

[Evaluation of electrical characteristics]
Next, an electrophotographic characteristic evaluation apparatus prepared in accordance with the standard of the Electrophotographic Society for these electrophotographic photoreceptors Q1 to Q7 (basic and applied electrophotographic technology, edited by the Electrophotographic Society, Corona, pages 404 to 405) And mounted on a photoconductor characteristic measuring machine, and evaluated under the environment of 25 ° C./50% of the electric characteristics by the cycle of charging (minus polarity), exposure, potential measurement, and static elimination according to the following procedure.

The photosensitive member is charged so that the initial surface potential is −600 V, the halogen lamp is irradiated with monochromatic light of 780 nm by an interference filter, and the exposure light is irradiated at an intensity of 1.0 μJ / cm ^2. The post-exposure surface potential (VL1) after 100 ms was measured (−V). When the exposure light is irradiated at an intensity of 1.0 μJ / cm ² after 10,000 cycles of charging (negative polarity), exposure, potential measurement, and static elimination in an environment of 25 ° C./50%. The post-exposure surface potential (VL2) after 100 ms was measured (−V). Also, when the exposure light is irradiated at an intensity of 1.0 μJ / cm ² after 10,000 cycles of charging (negative polarity), exposure, potential measurement, and static elimination in an environment of 35 ° C./85%. The post-exposure surface potential (VL3) after 100 ms was measured (−V). The measurement data is shown in Table-2.

[Image evaluation]
Next, the photoconductors Q1 to Q7 are mounted on a commercially available color laser printer (MPC2200, manufactured by Ricoh), and a print pattern partially including a black solid image is printed on A4 paper in an environment of 25 ° C./50%. After printing, the image after 500 sheets was visually evaluated. As for images having 500 images, the images after 6000 images were also visually evaluated. The evaluation data is shown in Table-3.

[Mobility measurement]
The hole mobility at a temperature of 21 ° C. in the electric field strength of 2 × 10 ⁵ (V / cm) of the obtained photoreceptors Q1 to Q7 was determined by the TOF (Time-of-flight) method. These results are shown in Table-1.

As can be seen from Table-3, the photoreceptor (Q1, Q2, Q3, Q6) in which the outermost surface layer contains silica particles having an average primary particle diameter of 0.2 to 1 μm or less can suppress filming. A good image is obtained. In particular, a photoconductor (Q1, Q2, Q6) having a silica content of 5.0 wt% or more.
) Was particularly good with no filming image observed even after 6000 sheets were printed.
Filming was severe in the photoreceptors (Q4, Q5) in which the outermost surface layer did not contain silica particles having an average primary particle diameter of 0.2 to 1 μm or less. In addition, filming images were observed on the photoreceptor (Q7) containing silica particles but having an average primary particle diameter of less than 0.2 μm, and good images were not obtained.

The outermost surface layer contains silica particles having an average primary particle diameter of 0.2 μm to 1 μm, and the hole mobility of the outermost surface layer is 2.0 × 10 ⁻⁵ cm ² / V · s or less (Q6). The initial electrical characteristics were good, but the VL after repetition was large. Even when silica particles with an average primary particle size of 0.2 μm to 1 μm are contained in the outermost surface layer, when the hole mobility of the outermost surface layer is as fast as 2.0 × 10 ⁻⁵ cm 2 / V · s or more, 25 ° C. / In a 50%, 35 ° C / 85% environment, the increase in residual potential (VL) is small even when charging (minus polarity), exposure, potential measurement, and static elimination cycles are repeated. The reason is not clear, but when charging (minus polarity), exposure, potential measurement, and static elimination are repeated while silica particles are usually present, a charge trap site is formed in the vicinity of the silica interface. It rises. However, if the hole mobility at an air temperature of 21 ° C at an electric field strength of 2 × 10 ⁵ (V / cm) is very fast, 2.0 × 10 ⁻⁵ cm ² / V · s or more, the charge trap site is Even if formed, since the mobility of holes is fast, the holes are not easily trapped, and the residual potential (VL) does not easily rise even if the above-described repetition is performed.

When the average primary particle diameter of the silica particles is less than 0.2 μm, the particles are small, so there is no obstacle to the movement of charges. However, when the particles are large, the charges are hindered and must be detoured (the trap site). Therefore, a mobility that does not matter the size of the particles is required.
The photoreceptors Q1, Q2, and Q3 are excellent in initial electrical characteristics, are excellent in repeated electrical characteristics, and are excellent in image characteristics (filming resistance).

Claims (7)

An electrophotographic photosensitive member having at least a charge generation layer and a charge transport layer in this order on a conductive substrate, wherein the charge transport layer is a single layer and an outermost surface layer, wherein the charge transport layer is at least a charge transport material and a binder resin And silica particles having an average primary particle size of 0.2 to 1 μm, the silica particles are 5 to 15 wt% of the entire charge transport layer, and the hole mobility of the charge transport layer is an electric field strength of 2.0 × 10 An electrophotographic photosensitive member characterized by being 2.0 × 10 ⁻⁵ cm ² / V · s or more at ⁵ V / cm and an air temperature of 21 ° C. 2. The electrophotographic photosensitive member according to claim 1, wherein the average primary particle size of the silica particles is 0.3 to 0.9 [mu] m. The electrophotographic photosensitive member according to claim 1 or 2, characterized in that the silica particles are surface treated with a reactive organosilicon compound. The electrophotographic photosensitive member according to any one of claims 1 to 3, the film thickness of the charge transport layer is equal to or is 10μm or more. Charge polarizability alpha of the charge transport material is a α> 100 (Å ^3), dipole moment P, characterized in that a P <1.60 (D), any of claim 1-4 2. The electrophotographic photosensitive member according to item 1. Using an electrophotographic photosensitive member according to any one of claims 1 to 5, the image forming apparatus. A cartridge for an image forming apparatus using the electrophotographic photosensitive member according to any one of claims 1 to 5 .

Images